<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        header {
            background-color: red;
            height: 100px;
        }

        section {
            background-color: blue;
            height: 300px;
            /* width: 1200px; */
        }

        footer {
            background-color: green;
            height: 200px;
        }

        section nav {
            background-color: gray;
            /* display: inline-block; */
            width: 30%;
            float: left;
        }

        section article {
            background-color: aquamarine;
            /* display: inline-block; */
            /* margin-left: 20px; */
            width: 70%;
            height: 300px;
            float: left;
        }
     
    </style>
</head>

<body>
    <header>
        头部
    </header>
    <section>
        <nav>
            导航
        </nav>
        <article>
            正文
        </article>
    </section>
    <footer>
        尾部
    </footer>
</body>

</html>